Question

Every year in our country about $25,000$ people are dead and $5,00,000$ more are injured as a result of drunk driving. In spite of efforts to educate the public about the dangers of driving while intoxicated and stiffer penalties for drunk driving offences, law enforcement agencies still have to devote a great deal of work to remove drunk drivers from roads.

The police often use a device called a breath analyser to test drivers suspected of being drunk. The chemical basis of this device is a redox reaction. A sample of the driver's breath is drawn into the breath analyser, where it is treated with an acidic solution of potassium dichromate.

$3C{H}_{3}C{H}_{2}OH+2K_{2}C{r}_2{O}_7+8H_{2}S{O}_4\to$ $3C{H}_{3}COOH+2C{r}_2(S{O}_4{)}_3+2K_{2}S{O}_4+11H_{2}O$

The driver's blood-alcohol level can be determined readily by measuring the degree of this colour change (read from a calibrated meter on the instrument). The current legal limit of blood alcohol content is $0.1$ percentage by mass. Anything higher constitutes intoxication.

The alcohol content in a $10.0$ g sample of blood from a driver required $4.23$ mL of $0.07654M{K}_{2}C{r}_2{O}_7$ for titration. Should the police prosecute the individual for drunken driving?

• A. Yes
• B. No
• C. Nothing can be predicted
• D. None of the above

Answer 1

The correct option is A Yes

Number of moles of $K_{2}C{r}_2{O}_7$ required $=\frac{4.23\times 0.07654}{1000}=3.24\times {10}^{-4}mol$

The reaction is as follows:

$3C{H}_{3}C{H}_{2}OH+2K_{2}C{r}_2{O}_7+8H_{2}S{O}_4\to 3C{H}_{3}COOH+2C{r}_2(S{O}_4{)}_3+2K_{2}S{O}_4+11H_{2}O$

Number of moles of $C{H}_{3}C{H}_{2}OH$ $=3.24\times {10}^{-4}\times \frac{3}{2}$ $=4.86\times {10}^{-4}$ $=0.0224$ g $C{H}_{3}C{H}_{2}OH$ in $10$ g of sample

$0.224\%$ is greater than legal limit $0.1$.

So, police should prosecute the individual for drunken driving.

Hence, the correct answer is $\left(A\right)$.